Activated carbon is made of wood, coal, petroleum coke and other carbon-containing raw materials by pyrolysis, activation processing preparation, has developed pore structure, large specific surface area and rich surface chemical groups, the general name of carbon materials with strong specific adsorption capacity.

It is usually powdery or granular porous amorphous carbon with strong adsorption capacity. By solid carbon (such as coal, wood, hard fruit shell, fruit pit, resin, etc.) in the isolation of air under the condition of 600 ~ 900℃ high temperature carbonization, and then under the condition of 400 ~ 900℃ with air, carbon dioxide, water vapor or a mixture of three gas after oxidation activation.

Carbonization volatilizes substances other than carbon, and oxidation activation can further remove residual volatile substances, generate new and expand the original pores, improve the micropore structure, and increase activity. Activated carbon at low temperature (400℃) is called L-carbon, activated carbon at high temperature (900℃) is called H-carbon. H- carbon must be cooled in an inert atmosphere, or it will be changed to L- carbon. Activated carbon adsorption performance and oxidation activation gas chemical properties and concentration, activation temperature, degree of activation, activated carbon inorganic composition and content and other factors, mainly depends on the nature of activated gas and activation temperature.

The carbon content, specific surface area, ash content of activated carbon and pH value of aqueous suspension increased with the increase of activation temperature. The higher the activation temperature, the more complete the residual volatile matter volatilization, the more developed the micropore structure, the larger the specific surface area and adsorption activity.

The ash composition and content of activated carbon have great influence on the adsorption activity of carbon. Ash is mainly composed of K2O, Na2O, CaO, MgO, Fe2O3, Al2O3, P2O5, SO3, Cl-, etc. The ash content is related to the raw material of activated carbon, and with the removal of volatiles in carbon, the ash content in carbon increases.

By 2007, the annual output of activated carbon in the world reached 900kt, of which coal-based activated carbon accounted for more than 2/3 of the total output. China's annual output has exceeded 400kt, ranking the first in the world. The United States, Japan and other major activated carbon producers in the world.